(a) Field of the Invention
This invention relates to an improved method for preparing 3-(4-pyridinyl)aniline, an intermediate for preparing rosoxacin, an antibacterial agent.
(b) Description of the Prior Art
Gelotte et al U.S. Pat. Nos. 4,026,900 and 4,075,217 disclose, and 4,075,217 claims, the process of heating the oxime of 3-(4-pyridinyl)-2-cyclohexen-1-one with an acetylating agent to produce the resulting O-acetyl oxime and then heating the O-acetyl oxime under acidic conditions, preferably in the presence of a strong mineral acid. The acetylation and subsequent heating steps were preferably run in combination by heating the oxime with acetic acid, acetic anhydride and hydrogen halide, preferably hydrogen chloride gas. The reaction was run in the range of about 80.degree. to 140.degree. C., preferably 100.degree. to 120.degree. C. The N-acetyl-3-(4-pyridinyl)aniline was then hydrolyzed to produce 3-(4-pyridinyl)aniline, an intermediate for preparing rosoxacin a known antibacterial agent.
Newman and Hung [J. Org. Chem. 38, 4073-4074 (1973)] showed the conversion of certain oximes of .alpha.-tetralones (7-methyl- and 7-chloro-.alpha.-tetralones) to the corresponding N-(1-naphthyl)acetamides by heating the oxime in acetic anhydride and anhydrous phosphoric acid at 80.degree. C. for thirty minutes. Unsuccessful results due to side-reactions resulted using these reaction conditions with the oxime of 6-methoxy-.alpha.-tetralone. Phosphorus pentoxide was used to prepare the anhydrous phosphoric acid.